A 3rd generation partnership project (3GPP) long term evolution (LTE) which is improved universal mobile telecommunications system (UMTS) is introduced as 3GPP release 8. The 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in a lower link and uses single carrier-frequency division multiple access (SC-FDMA) in an upper link. A multiple input multiple output (MIMO) having maximum four antennas is employed. Recently, a discussion on LTE-Advanced (LTE-A) which is evolved 3GPP LTE is being developed.
A minimization of driving tests (MDT) is to test by operators for coverage optimization by using a terminal instead of a vehicle. The coverage is varied according to a location of a base station, an arrangement of neighboring buildings, and a use environment of a user. Therefore, the operator needs to periodically perform a driving test, which consumes a lot of cost and resources. The MDT measures the coverage by the operator using the terminal.
The operator may draft a coverage map indicating availability of a service over an overall service area of the operator and distribution of a quality of the service by summarizing the MDT measurement received from a plurality of terminals, thereby utilizing the coverage map for operating and optimizing the network. For example, when a coverage problem of a particular area is reported from the terminal, the operator may increase transmission power of the base station which provides a service to the corresponding area to expand the coverage of a corresponding area cell.
A result of the MDT measurement is information not needed for the terminal but information used for optimizing the network. Therefore, the terminal may not learn whether the MDT measurement result is important for optimizing the network or for other purpose.
As a result, when the network does not send a command for reporting the logged measurement to the terminal or delays in sending the command, the stored logged measurement may not be reported to the network and may be lost.